package test33;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: ws
 * Date: 2023-04-26
 * Time: 22:22
 */
import java.io.*;
//https://www.nowcoder.com/practice/3549ff22ae2c4da4890e9ad0ccb6150d?tab=note
public class Main {
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

    public static void main(String[] args) throws IOException {
        String str = null;
        //1、1、2、3、5、8、13、21、34、
        while ((str = br.readLine()) != null) {
            String[] strs = str.split(" ");
            long from = Long.parseLong(strs[0]);
            long to = Long.parseLong(strs[1]) - from + 1;
            long a = 0;
            long b = 1;
            for (long i = 0; i < from; i++) {
                long temp = b;
                b += a;
                a = temp;
            }
            long sum = a;
            for (long i = 1; i < to; i++) {
                long temp = b;
                b += a;
                a = temp;
                sum += a;
            }
            bw.write(sum + "\n");
            bw.flush();
        }
        bw.close();
        br.close();
    }
}
